Im Zentrum der Arbeiten soll die Chaos- und Kohärenzkontrolle von Halbleiterlasern mit gegenseitiger optischer Kopplung stehen. Diese Fragestellung ist von erheblicher praktischer Relevanz, da Rauschen und chaotisches Verhalten generelle Probleme in der optischen Hochgeschwindigkeitskommunikation sind. Die Kontrolle von optischen Systemen mit komplexer Selbstorganisation stellt aber auch aus grundsätzlicher Sicht Neuland dar. Hierfür geeignete Konzepte sind bisher weder überzeugend theoretisch beschrieben noch experimentell umgesetzt.
We describe the basic ideas behind the concept of distributed
feedback (DFB) lasers with short optical feedback for the
generation of high-frequency self-pulsations and show the theoretical
background describing realized devices. It is predicted by
theory that the self-pulsation frequency increases with increasing
feedback strength. To provide evidence for this, we propose a novel
device design which employs an amplifier section in the integrated
feedback cavity of a DFB laser.We present results from numerical
simulations and experiments. It has been shown experimentally
that a continuous tuning of the self-pulsation frequency from 12
to 45 GHz can be adjusted via the control of the feedback strength.
The numerical simulations, which are in good accordance with experimental
investigations, give an explanation for a self-stabilizing
effect of the self-pulsations due to the additional carrier dynamic
in the integrated feedback cavity.
An in-depth theoretical as well as experimental analysis of the nonlinear dynamics in semiconductor lasers
with active optical feedback is presented. Use of a monolithically integrated multisection device of submillimeter
total length provides access to the short-cavity regime. By introducing an amplifier section as a special
feature, phase and strength of the feedback can be separately tuned. In this way, the number of modes involved
in the laser action can be adjusted. We predict and observe specific dynamical scenarios. Bifurcations mediate
various transitions in the device output, from single-mode steadystate to self-pulsation and between different
kinds of self-pulsations, reaching eventually chaotic behavior in the multimode limit.